Image: DC Comics
The New York Times has a fantastic interactive gallery featuring Al Jaffee's fold-ins for MAD magazine from the 1960s to the present.
This one above, titled "Who Wants to be President More Than Anything"
is from the June 1964 issue, with the captions of "Rich candidates Rockefeller and Goldwater would fight hard in any pre-convention debates, weakening unity, so nixing idea was best for party's chances to beat Johnson." When folded, the unmistakeable image of Richard Nixon emerged (it would be another 4 years before Nixon did indeed become president).